I've noticed that an Engineers Weapon and Condition damage when equipped with one of the Engineer exclusive weapons (Grenade Kit, Bomb Kit, Flamethrower, Elixir Gun, and Wrench) are calculated independently of the weapon they have equipped. In other words, the statistics of the equipped weapons don't have any impact on Weapon and Condition damage when I have an Engineer exclusive weapon equipped.
I tested this by equipping the Elixir Gun and comparing my damage when I had a Pistol and Shield equipped versus when I didn't. In both cases my weapon and condition damage were unchanged (244 and 130 respectively).
I find this very unusual, since it could result in my Engineer kit skills being considerably weaker than the skills of my non-Engineer weapons.
How is an Engineer's damage calculated when wielding one of the Engineer exclusive weapons?
Pistol and Shield
Elixir Gun with Pistol and Shield equipped
Elixir Gun without pistol and shield equipped